可见不重复

Question

I'm trying to repeat() an action in an observable but it is not performing it more than once.

Observable.create(new ObservableOnSubscribe<String>() {
        @Override
        public void subscribe(ObservableEmitter<String> e) throws Exception {
            // **** Code Here is not repeating ****
            e.onNext(pullMessagesFromServer());
        }
    })
    .repeat()
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .map(new Function<String, JSONArray>() {
        @Override
        public JSONArray apply(String s) throws Exception {
            return JsonParser.parseString(s);
        }
    })
    .subscribe(new Observer<JSONArray>() {
        @Override
        public void onNext(JSONArray arr) {
            // **** Code Here is not repeating ****
        }  
    });
}

What gives? Thanks! New to Rxjava and it's confusing me somewhat. :(

Answer 1

From my comment: repeat operates if the source completes. Add e.onComplete() .

Observable.create(new ObservableOnSubscribe<String>() {
        @Override
        public void subscribe(ObservableEmitter<String> e) throws Exception {
            // **** Code Here is not repeating ****
            e.onNext(pullMessagesFromServer());
            e.onComplete();
        }
    })
    .repeat()
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .map(new Function<String, JSONArray>() {
        @Override
        public JSONArray apply(String s) throws Exception {
            return JsonParser.parseString(s);
        }
    })
    .subscribe(new Observer<JSONArray>() {
        @Override
        public void onNext(JSONArray arr) {
            // **** Code Here is not repeating ****
        }  
    });
}

The reason for this is that the Observable protocol is potentially asynchronous, that is, events may arrive over time. Therefore, just because your code stopped signalling events, the library can't know there won't be any further events. You have to be explicit about indicating no more values will be emitted when using create() . Generally, you can use other factory methods such as fromCallable that will make sure a single generated value will be properly signaled:

Observable.fromCallable(new Callable<String>() {
        @Override
        public String call() throws Exception {
            // **** Code Here is not repeating ****
            return pullMessagesFromServer();
        }
    })
    .repeat()
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .map(new Function<String, JSONArray>() {
        @Override
        public JSONArray apply(String s) throws Exception {
            return JsonParser.parseString(s);
        }
    })
    .subscribe(new Observer<JSONArray>() {
        @Override
        public void onNext(JSONArray arr) {
            // **** Code Here is not repeating ****
        }  
    });
}